Water Quality – Bacteria
Water Quality – Bacteria
The standards for water quality (determined by health authorities) to ensure safe swimming have changed over the years.
Prior to 1986 the upper limit for E. coli or Faecal coliforms was 3000 organisms per 100ml sample size. This E. coli limit was in force to 2003. Guidelines were developed in June 2003 for Howard Springs Water Hole for assessing the suitability for swimming by visitors. These guidelines were developed with the assistance of the (the Northern Territory Government) Department of Health and used the Australian Standard for recreational water quality (developed in 1997).
These new water monitoring guidelines required the following action in response to measured water quality:
- Samples that are greater than 150 organisms – information about potential bacteria levels
- Greater than 600 organisms but les than 1000 organisms –Caution signs put in place recommending no swimming
- Greater than 1000 organisms – swimming prohibited
In 2007 the NT guidelines were further refined to reflect revised national guidelines for managing risks in recreational water. This revision concluded that a different bacteria was a better indicator of contamination and the allowable limits were revised as follows:
- Less than 50 enterococci and/or 200 E. coli – swimming allowed
- Greater than 200 enterrococci and/or greater than 200 E. coli - Caution required for swimming
- Greater than 200 enterococci and/or 500 E. coli – closed for swimming
So over the decades during which the waterhole has been used, parks authorities have measured and managed water quality against health guidelines which themselves have changed in respect of the harmful bacteria and the safe levels. The guidelines change because new information comes to hand on how to best protect the health and safety of all water users.
The daily sampling at Howard Springs now tests for both enterrococci and E. coli at present to obtain a relationship between the two test values.